CI fails trying to install `pip` package on `msys2`

[minhqdao]

Description

An error recently appeared while trying to install fypp using pip on msys2. The CI fails with the following error message:

Run pip install fypp
error: externally-managed-environment

× This environment is externally managed
╰─> To install Python packages system-wide, try 'pacman -S
    python-xyz', where xyz is the package you are trying to
    install.
    
    If you wish to install a non-MSYS2-packaged Python package,
    create a virtual environment using 'python -m venv path/to/venv'.
    Then use path/to/venv/bin/python and path/to/venv/bin/pip.

Expected Behaviour

fypp is installed without failing.

Version of stdlib

master

Platform and Architecture

Windows-MSYS2

Additional Information

No response

[zoziha]

@minhqdao, this seems to be caused by changes in Python and Pip. If we insist on using the system-level installation, we can pass the --break-system-packages parameter, such as:

pip install --break-system-packages fypp

Or use the virtual environment venv:

python3 -m venv path/to/venv
source <venv>/bin/activate
pip install fypp

[minhqdao]

That's correct. And if we take the venv route, we'd also need to make sure the venv is properly sourced for every subsequent run.

But as you pointed out in #854 (comment), it's probably alright to abandon msystem: msys altogether. I'll merge the PR so the CI stops failing.